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modules.nix
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modules.nix
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{ lib }:
let
inherit (lib)
all
any
attrByPath
attrNames
catAttrs
concatLists
concatMap
concatStringsSep
elem
filter
foldl'
getAttrFromPath
head
id
imap1
isAttrs
isBool
isFunction
isList
isString
length
mapAttrs
mapAttrsToList
mapAttrsRecursiveCond
min
optional
optionalAttrs
optionalString
recursiveUpdate
reverseList sort
setAttrByPath
types
warnIf
zipAttrsWith
;
inherit (lib.options)
isOption
mkOption
showDefs
showFiles
showOption
unknownModule
;
inherit (lib.strings)
isConvertibleWithToString
;
showDeclPrefix = loc: decl: prefix:
" - option(s) with prefix `${showOption (loc ++ [prefix])}' in module `${decl._file}'";
showRawDecls = loc: decls:
concatStringsSep "\n"
(sort (a: b: a < b)
(concatMap
(decl: map
(showDeclPrefix loc decl)
(attrNames decl.options)
)
decls
));
/* See https://nixos.org/manual/nixpkgs/unstable/#module-system-lib-evalModules
or file://./../doc/module-system/module-system.chapter.md
!!! Please think twice before adding to this argument list! The more
that is specified here instead of in the modules themselves the harder
it is to transparently move a set of modules to be a submodule of another
config (as the proper arguments need to be replicated at each call to
evalModules) and the less declarative the module set is. */
evalModules = evalModulesArgs@
{ modules
, prefix ? []
, # This should only be used for special arguments that need to be evaluated
# when resolving module structure (like in imports). For everything else,
# there's _module.args. If specialArgs.modulesPath is defined it will be
# used as the base path for disabledModules.
specialArgs ? {}
, # `class`:
# A nominal type for modules. When set and non-null, this adds a check to
# make sure that only compatible modules are imported.
class ? null
, # This would be remove in the future, Prefer _module.args option instead.
args ? {}
, # This would be remove in the future, Prefer _module.check option instead.
check ? true
}:
let
withWarnings = x:
lib.warnIf (evalModulesArgs?args) "The args argument to evalModules is deprecated. Please set config._module.args instead."
lib.warnIf (evalModulesArgs?check) "The check argument to evalModules is deprecated. Please set config._module.check instead."
x;
legacyModules =
optional (evalModulesArgs?args) {
config = {
_module.args = args;
};
}
++ optional (evalModulesArgs?check) {
config = {
_module.check = mkDefault check;
};
};
regularModules = modules ++ legacyModules;
# This internal module declare internal options under the `_module'
# attribute. These options are fragile, as they are used by the
# module system to change the interpretation of modules.
#
# When extended with extendModules or moduleType, a fresh instance of
# this module is used, to avoid conflicts and allow chaining of
# extendModules.
internalModule = rec {
_file = "lib/modules.nix";
key = _file;
options = {
_module.args = mkOption {
# Because things like `mkIf` are entirely useless for
# `_module.args` (because there's no way modules can check which
# arguments were passed), we'll use `lazyAttrsOf` which drops
# support for that, in turn it's lazy in its values. This means e.g.
# a `_module.args.pkgs = import (fetchTarball { ... }) {}` won't
# start a download when `pkgs` wasn't evaluated.
type = types.lazyAttrsOf types.raw;
# Only render documentation once at the root of the option tree,
# not for all individual submodules.
# Allow merging option decls to make this internal regardless.
${if prefix == []
then null # unset => visible
else "internal"} = true;
# TODO: Change the type of this option to a submodule with a
# freeformType, so that individual arguments can be documented
# separately
description = ''
Additional arguments passed to each module in addition to ones
like `lib`, `config`,
and `pkgs`, `modulesPath`.
This option is also available to all submodules. Submodules do not
inherit args from their parent module, nor do they provide args to
their parent module or sibling submodules. The sole exception to
this is the argument `name` which is provided by
parent modules to a submodule and contains the attribute name
the submodule is bound to, or a unique generated name if it is
not bound to an attribute.
Some arguments are already passed by default, of which the
following *cannot* be changed with this option:
- {var}`lib`: The nixpkgs library.
- {var}`config`: The results of all options after merging the values from all modules together.
- {var}`options`: The options declared in all modules.
- {var}`specialArgs`: The `specialArgs` argument passed to `evalModules`.
- All attributes of {var}`specialArgs`
Whereas option values can generally depend on other option values
thanks to laziness, this does not apply to `imports`, which
must be computed statically before anything else.
For this reason, callers of the module system can provide `specialArgs`
which are available during import resolution.
For NixOS, `specialArgs` includes
{var}`modulesPath`, which allows you to import
extra modules from the nixpkgs package tree without having to
somehow make the module aware of the location of the
`nixpkgs` or NixOS directories.
```
{ modulesPath, ... }: {
imports = [
(modulesPath + "/profiles/minimal.nix")
];
}
```
For NixOS, the default value for this option includes at least this argument:
- {var}`pkgs`: The nixpkgs package set according to
the {option}`nixpkgs.pkgs` option.
'';
};
_module.check = mkOption {
type = types.bool;
internal = true;
default = true;
description = "Whether to check whether all option definitions have matching declarations.";
};
_module.freeformType = mkOption {
type = types.nullOr types.optionType;
internal = true;
default = null;
description = ''
If set, merge all definitions that don't have an associated option
together using this type. The result then gets combined with the
values of all declared options to produce the final `
config` value.
If this is `null`, definitions without an option
will throw an error unless {option}`_module.check` is
turned off.
'';
};
_module.specialArgs = mkOption {
readOnly = true;
internal = true;
description = ''
Externally provided module arguments that can't be modified from
within a configuration, but can be used in module imports.
'';
};
};
config = {
_module.args = {
inherit extendModules;
moduleType = type;
};
_module.specialArgs = specialArgs;
};
};
merged =
let collected = collectModules
class
(specialArgs.modulesPath or "")
(regularModules ++ [ internalModule ])
({ inherit lib options config specialArgs; } // specialArgs);
in mergeModules prefix (reverseList collected);
options = merged.matchedOptions;
config =
let
# For definitions that have an associated option
declaredConfig = mapAttrsRecursiveCond (v: ! isOption v) (_: v: v.value) options;
# If freeformType is set, this is for definitions that don't have an associated option
freeformConfig =
let
defs = map (def: {
file = def.file;
value = setAttrByPath def.prefix def.value;
}) merged.unmatchedDefns;
in if defs == [] then {}
else declaredConfig._module.freeformType.merge prefix defs;
in if declaredConfig._module.freeformType == null then declaredConfig
# Because all definitions that had an associated option ended in
# declaredConfig, freeformConfig can only contain the non-option
# paths, meaning recursiveUpdate will never override any value
else recursiveUpdate freeformConfig declaredConfig;
checkUnmatched =
if config._module.check && config._module.freeformType == null && merged.unmatchedDefns != [] then
let
firstDef = head merged.unmatchedDefns;
baseMsg =
let
optText = showOption (prefix ++ firstDef.prefix);
defText =
builtins.addErrorContext
"while evaluating the error message for definitions for `${optText}', which is an option that does not exist"
(builtins.addErrorContext
"while evaluating a definition from `${firstDef.file}'"
( showDefs [ firstDef ])
);
in
"The option `${optText}' does not exist. Definition values:${defText}";
in
if attrNames options == [ "_module" ]
# No options were declared at all (`_module` is built in)
# but we do have unmatched definitions, and no freeformType (earlier conditions)
then
let
optionName = showOption prefix;
in
if optionName == ""
then throw ''
${baseMsg}
It seems as if you're trying to declare an option by placing it into `config' rather than `options'!
''
else
throw ''
${baseMsg}
However there are no options defined in `${showOption prefix}'. Are you sure you've
declared your options properly? This can happen if you e.g. declared your options in `types.submodule'
under `config' rather than `options'.
''
else throw baseMsg
else null;
checked = builtins.seq checkUnmatched;
extendModules = extendArgs@{
modules ? [],
specialArgs ? {},
prefix ? [],
}:
evalModules (evalModulesArgs // {
inherit class;
modules = regularModules ++ modules;
specialArgs = evalModulesArgs.specialArgs or {} // specialArgs;
prefix = extendArgs.prefix or evalModulesArgs.prefix or [];
});
type = lib.types.submoduleWith {
inherit modules specialArgs class;
};
result = withWarnings {
_type = "configuration";
options = checked options;
config = checked (removeAttrs config [ "_module" ]);
_module = checked (config._module);
inherit extendModules type;
class = class;
};
in result;
# collectModules :: (class: String) -> (modulesPath: String) -> (modules: [ Module ]) -> (args: Attrs) -> [ Module ]
#
# Collects all modules recursively through `import` statements, filtering out
# all modules in disabledModules.
collectModules = class: let
# Like unifyModuleSyntax, but also imports paths and calls functions if necessary
loadModule = args: fallbackFile: fallbackKey: m:
if isFunction m then
unifyModuleSyntax fallbackFile fallbackKey (applyModuleArgs fallbackKey m args)
else if isAttrs m then
if m._type or "module" == "module" then
unifyModuleSyntax fallbackFile fallbackKey m
else if m._type == "if" || m._type == "override" then
loadModule args fallbackFile fallbackKey { config = m; }
else
throw (
"Could not load a value as a module, because it is of type ${lib.strings.escapeNixString m._type}"
+ lib.optionalString (fallbackFile != unknownModule) ", in file ${toString fallbackFile}."
+ lib.optionalString (m._type == "configuration") " If you do intend to import this configuration, please only import the modules that make up the configuration. You may have to create a `let` binding, file or attribute to give yourself access to the relevant modules.\nWhile loading a configuration into the module system is a very sensible idea, it can not be done cleanly in practice."
# Extended explanation: That's because a finalized configuration is more than just a set of modules. For instance, it has its own `specialArgs` that, by the nature of `specialArgs` can't be loaded through `imports` or the the `modules` argument. So instead, we have to ask you to extract the relevant modules and use those instead. This way, we keep the module system comparatively simple, and hopefully avoid a bad surprise down the line.
)
else if isList m then
let defs = [{ file = fallbackFile; value = m; }]; in
throw "Module imports can't be nested lists. Perhaps you meant to remove one level of lists? Definitions: ${showDefs defs}"
else unifyModuleSyntax (toString m) (toString m) (applyModuleArgsIfFunction (toString m) (import m) args);
checkModule =
if class != null
then
m:
if m._class != null -> m._class == class
then m
else
throw "The module ${m._file or m.key} was imported into ${class} instead of ${m._class}."
else
m: m;
/*
Collects all modules recursively into the form
{
disabled = [ <list of disabled modules> ];
# All modules of the main module list
modules = [
{
key = <key1>;
module = <module for key1>;
# All modules imported by the module for key1
modules = [
{
key = <key1-1>;
module = <module for key1-1>;
# All modules imported by the module for key1-1
modules = [ ... ];
}
...
];
}
...
];
}
*/
collectStructuredModules =
let
collectResults = modules: {
disabled = concatLists (catAttrs "disabled" modules);
inherit modules;
};
in parentFile: parentKey: initialModules: args: collectResults (imap1 (n: x:
let
module = checkModule (loadModule args parentFile "${parentKey}:anon-${toString n}" x);
collectedImports = collectStructuredModules module._file module.key module.imports args;
in {
key = module.key;
module = module;
modules = collectedImports.modules;
disabled = (if module.disabledModules != [] then [{ file = module._file; disabled = module.disabledModules; }] else []) ++ collectedImports.disabled;
}) initialModules);
# filterModules :: String -> { disabled, modules } -> [ Module ]
#
# Filters a structure as emitted by collectStructuredModules by removing all disabled
# modules recursively. It returns the final list of unique-by-key modules
filterModules = modulesPath: { disabled, modules }:
let
moduleKey = file: m:
if isString m
then
if builtins.substring 0 1 m == "/"
then m
else toString modulesPath + "/" + m
else if isConvertibleWithToString m
then
if m?key && m.key != toString m
then
throw "Module `${file}` contains a disabledModules item that is an attribute set that can be converted to a string (${toString m}) but also has a `.key` attribute (${m.key}) with a different value. This makes it ambiguous which module should be disabled."
else
toString m
else if m?key
then
m.key
else if isAttrs m
then throw "Module `${file}` contains a disabledModules item that is an attribute set, presumably a module, that does not have a `key` attribute. This means that the module system doesn't have any means to identify the module that should be disabled. Make sure that you've put the correct value in disabledModules: a string path relative to modulesPath, a path value, or an attribute set with a `key` attribute."
else throw "Each disabledModules item must be a path, string, or a attribute set with a key attribute, or a value supported by toString. However, one of the disabledModules items in `${toString file}` is none of that, but is of type ${builtins.typeOf m}.";
disabledKeys = concatMap ({ file, disabled }: map (moduleKey file) disabled) disabled;
keyFilter = filter (attrs: ! elem attrs.key disabledKeys);
in map (attrs: attrs.module) (builtins.genericClosure {
startSet = keyFilter modules;
operator = attrs: keyFilter attrs.modules;
});
in modulesPath: initialModules: args:
filterModules modulesPath (collectStructuredModules unknownModule "" initialModules args);
/* Wrap a module with a default location for reporting errors. */
setDefaultModuleLocation = file: m:
{ _file = file; imports = [ m ]; };
/* Massage a module into canonical form, that is, a set consisting
of ‘options’, ‘config’ and ‘imports’ attributes. */
unifyModuleSyntax = file: key: m:
let
addMeta = config: if m ? meta
then mkMerge [ config { meta = m.meta; } ]
else config;
addFreeformType = config: if m ? freeformType
then mkMerge [ config { _module.freeformType = m.freeformType; } ]
else config;
in
if m ? config || m ? options then
let badAttrs = removeAttrs m ["_class" "_file" "key" "disabledModules" "imports" "options" "config" "meta" "freeformType"]; in
if badAttrs != {} then
throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'. This is caused by introducing a top-level `config' or `options' attribute. Add configuration attributes immediately on the top level instead, or move all of them (namely: ${toString (attrNames badAttrs)}) into the explicit `config' attribute."
else
{ _file = toString m._file or file;
_class = m._class or null;
key = toString m.key or key;
disabledModules = m.disabledModules or [];
imports = m.imports or [];
options = m.options or {};
config = addFreeformType (addMeta (m.config or {}));
}
else
# shorthand syntax
lib.throwIfNot (isAttrs m) "module ${file} (${key}) does not look like a module."
{ _file = toString m._file or file;
_class = m._class or null;
key = toString m.key or key;
disabledModules = m.disabledModules or [];
imports = m.require or [] ++ m.imports or [];
options = {};
config = addFreeformType (removeAttrs m ["_class" "_file" "key" "disabledModules" "require" "imports" "freeformType"]);
};
applyModuleArgsIfFunction = key: f: args@{ config, options, lib, ... }:
if isFunction f then applyModuleArgs key f args else f;
applyModuleArgs = key: f: args@{ config, options, lib, ... }:
let
# Module arguments are resolved in a strict manner when attribute set
# deconstruction is used. As the arguments are now defined with the
# config._module.args option, the strictness used on the attribute
# set argument would cause an infinite loop, if the result of the
# option is given as argument.
#
# To work-around the strictness issue on the deconstruction of the
# attributes set argument, we create a new attribute set which is
# constructed to satisfy the expected set of attributes. Thus calling
# a module will resolve strictly the attributes used as argument but
# not their values. The values are forwarding the result of the
# evaluation of the option.
context = name: ''while evaluating the module argument `${name}' in "${key}":'';
extraArgs = builtins.mapAttrs (name: _:
builtins.addErrorContext (context name)
(args.${name} or config._module.args.${name})
) (lib.functionArgs f);
# Note: we append in the opposite order such that we can add an error
# context on the explicit arguments of "args" too. This update
# operator is used to make the "args@{ ... }: with args.lib;" notation
# works.
in f (args // extraArgs);
/* Merge a list of modules. This will recurse over the option
declarations in all modules, combining them into a single set.
At the same time, for each option declaration, it will merge the
corresponding option definitions in all machines, returning them
in the ‘value’ attribute of each option.
This returns a set like
{
# A recursive set of options along with their final values
matchedOptions = {
foo = { _type = "option"; value = "option value of foo"; ... };
bar.baz = { _type = "option"; value = "option value of bar.baz"; ... };
...
};
# A list of definitions that weren't matched by any option
unmatchedDefns = [
{ file = "file.nix"; prefix = [ "qux" ]; value = "qux"; }
...
];
}
*/
mergeModules = prefix: modules:
mergeModules' prefix modules
(concatMap (m: map (config: { file = m._file; inherit config; }) (pushDownProperties m.config)) modules);
mergeModules' = prefix: modules: configs:
let
# an attrset 'name' => list of submodules that declare ‘name’.
declsByName =
zipAttrsWith
(n: concatLists)
(map
(module: let subtree = module.options; in
if !(builtins.isAttrs subtree) then
throw ''
An option declaration for `${builtins.concatStringsSep "." prefix}' has type
`${builtins.typeOf subtree}' rather than an attribute set.
Did you mean to define this outside of `options'?
''
else
mapAttrs
(n: option:
[{ inherit (module) _file; pos = builtins.unsafeGetAttrPos n subtree; options = option; }]
)
subtree
)
modules);
# The root of any module definition must be an attrset.
checkedConfigs =
assert
lib.all
(c:
# TODO: I have my doubts that this error would occur when option definitions are not matched.
# The implementation of this check used to be tied to a superficially similar check for
# options, so maybe that's why this is here.
isAttrs c.config || throw ''
In module `${c.file}', you're trying to define a value of type `${builtins.typeOf c.config}'
rather than an attribute set for the option
`${builtins.concatStringsSep "." prefix}'!
This usually happens if `${builtins.concatStringsSep "." prefix}' has option
definitions inside that are not matched. Please check how to properly define
this option by e.g. referring to `man 5 configuration.nix'!
''
)
configs;
configs;
# an attrset 'name' => list of submodules that define ‘name’.
pushedDownDefinitionsByName =
zipAttrsWith
(n: concatLists)
(map
(module:
mapAttrs
(n: value:
map (config: { inherit (module) file; inherit config; }) (pushDownProperties value)
)
module.config
)
checkedConfigs);
# extract the definitions for each loc
rawDefinitionsByName =
zipAttrsWith
(n: concatLists)
(map
(module:
mapAttrs
(n: value:
[{ inherit (module) file; inherit value; }]
)
module.config
)
checkedConfigs);
# Convert an option tree decl to a submodule option decl
optionTreeToOption = decl:
if isOption decl.options
then decl
else decl // {
options = mkOption {
type = types.submoduleWith {
modules = [ { options = decl.options; } ];
# `null` is not intended for use by modules. It is an internal
# value that means "whatever the user has declared elsewhere".
# This might become obsolete with https://github.com/NixOS/nixpkgs/issues/162398
shorthandOnlyDefinesConfig = null;
};
};
};
resultsByName = mapAttrs (name: decls:
# We're descending into attribute ‘name’.
let
loc = prefix ++ [name];
defns = pushedDownDefinitionsByName.${name} or [];
defns' = rawDefinitionsByName.${name} or [];
optionDecls = filter
(m: m.options?_type
&& (m.options._type == "option"
|| throwDeclarationTypeError loc m.options._type m._file
)
)
decls;
in
if length optionDecls == length decls then
let opt = fixupOptionType loc (mergeOptionDecls loc decls);
in {
matchedOptions = evalOptionValue loc opt defns';
unmatchedDefns = [];
}
else if optionDecls != [] then
if all (x: x.options.type.name or null == "submodule") optionDecls
# Raw options can only be merged into submodules. Merging into
# attrsets might be nice, but ambiguous. Suppose we have
# attrset as a `attrsOf submodule`. User declares option
# attrset.foo.bar, this could mean:
# a. option `bar` is only available in `attrset.foo`
# b. option `foo.bar` is available in all `attrset.*`
# c. reject and require "<name>" as a reminder that it behaves like (b).
# d. magically combine (a) and (c).
# All of the above are merely syntax sugar though.
then
let opt = fixupOptionType loc (mergeOptionDecls loc (map optionTreeToOption decls));
in {
matchedOptions = evalOptionValue loc opt defns';
unmatchedDefns = [];
}
else
let
nonOptions = filter (m: !isOption m.options) decls;
in
throw "The option `${showOption loc}' in module `${(lib.head optionDecls)._file}' would be a parent of the following options, but its type `${(lib.head optionDecls).options.type.description or "<no description>"}' does not support nested options.\n${
showRawDecls loc nonOptions
}"
else
mergeModules' loc decls defns) declsByName;
matchedOptions = mapAttrs (n: v: v.matchedOptions) resultsByName;
# an attrset 'name' => list of unmatched definitions for 'name'
unmatchedDefnsByName =
# Propagate all unmatched definitions from nested option sets
mapAttrs (n: v: v.unmatchedDefns) resultsByName
# Plus the definitions for the current prefix that don't have a matching option
// removeAttrs rawDefinitionsByName (attrNames matchedOptions);
in {
inherit matchedOptions;
# Transforms unmatchedDefnsByName into a list of definitions
unmatchedDefns =
if configs == []
then
# When no config values exist, there can be no unmatched config, so
# we short circuit and avoid evaluating more _options_ than necessary.
[]
else
concatLists (mapAttrsToList (name: defs:
map (def: def // {
# Set this so we know when the definition first left unmatched territory
prefix = [name] ++ (def.prefix or []);
}) defs
) unmatchedDefnsByName);
};
throwDeclarationTypeError = loc: actualTag: file:
let
name = lib.strings.escapeNixIdentifier (lib.lists.last loc);
path = showOption loc;
depth = length loc;
paragraphs = [
"In module ${file}: expected an option declaration at option path `${path}` but got an attribute set with type ${actualTag}"
] ++ optional (actualTag == "option-type") ''
When declaring an option, you must wrap the type in a `mkOption` call. It should look somewhat like:
${comment}
${name} = lib.mkOption {
description = ...;
type = <the type you wrote for ${name}>;
...
};
'';
# Ideally we'd know the exact syntax they used, but short of that,
# we can only reliably repeat the last. However, we repeat the
# full path in a non-misleading way here, in case they overlook
# the start of the message. Examples attract attention.
comment = optionalString (depth > 1) "\n # ${showOption loc}";
in
throw (concatStringsSep "\n\n" paragraphs);
/* Merge multiple option declarations into a single declaration. In
general, there should be only one declaration of each option.
The exception is the ‘options’ attribute, which specifies
sub-options. These can be specified multiple times to allow one
module to add sub-options to an option declared somewhere else
(e.g. multiple modules define sub-options for ‘fileSystems’).
'loc' is the list of attribute names where the option is located.
'opts' is a list of modules. Each module has an options attribute which
correspond to the definition of 'loc' in 'opt.file'. */
mergeOptionDecls =
loc: opts:
foldl' (res: opt:
let t = res.type;
t' = opt.options.type;
mergedType = t.typeMerge t'.functor;
typesMergeable = mergedType != null;
typeSet = if (bothHave "type") && typesMergeable
then { type = mergedType; }
else {};
bothHave = k: opt.options ? ${k} && res ? ${k};
in
if bothHave "default" ||
bothHave "example" ||
bothHave "description" ||
bothHave "apply" ||
(bothHave "type" && (! typesMergeable))
then
throw "The option `${showOption loc}' in `${opt._file}' is already declared in ${showFiles res.declarations}."
else
let
getSubModules = opt.options.type.getSubModules or null;
submodules =
if getSubModules != null then map (setDefaultModuleLocation opt._file) getSubModules ++ res.options
else res.options;
in opt.options // res //
{ declarations = res.declarations ++ [opt._file];
# In the case of modules that are generated dynamically, we won't
# have exact declaration lines; fall back to just the file being
# evaluated.
declarationPositions = res.declarationPositions
++ (if opt.pos != null
then [opt.pos]
else [{ file = opt._file; line = null; column = null; }]);
options = submodules;
} // typeSet
) { inherit loc; declarations = []; declarationPositions = []; options = []; } opts;
/* Merge all the definitions of an option to produce the final
config value. */
evalOptionValue = loc: opt: defs:
let
# Add in the default value for this option, if any.
defs' =
(optional (opt ? default)
{ file = head opt.declarations; value = mkOptionDefault opt.default; }) ++ defs;
# Handle properties, check types, and merge everything together.
res =
if opt.readOnly or false && length defs' > 1 then
let
# For a better error message, evaluate all readOnly definitions as
# if they were the only definition.
separateDefs = map (def: def // {
value = (mergeDefinitions loc opt.type [ def ]).mergedValue;
}) defs';
in throw "The option `${showOption loc}' is read-only, but it's set multiple times. Definition values:${showDefs separateDefs}"
else
mergeDefinitions loc opt.type defs';
# Apply the 'apply' function to the merged value. This allows options to
# yield a value computed from the definitions
value = if opt ? apply then opt.apply res.mergedValue else res.mergedValue;
warnDeprecation =
warnIf (opt.type.deprecationMessage != null)
"The type `types.${opt.type.name}' of option `${showOption loc}' defined in ${showFiles opt.declarations} is deprecated. ${opt.type.deprecationMessage}";
in warnDeprecation opt //
{ value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
inherit (res.defsFinal') highestPrio;
definitions = map (def: def.value) res.defsFinal;
files = map (def: def.file) res.defsFinal;
definitionsWithLocations = res.defsFinal;
inherit (res) isDefined;
# This allows options to be correctly displayed using `${options.path.to.it}`
__toString = _: showOption loc;
};
# Merge definitions of a value of a given type.
mergeDefinitions = loc: type: defs: rec {
defsFinal' =
let
# Process mkMerge and mkIf properties.
defs' = concatMap (m:
map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))
) defs;
# Process mkOverride properties.
defs'' = filterOverrides' defs';
# Sort mkOrder properties.
defs''' =
# Avoid sorting if we don't have to.
if any (def: def.value._type or "" == "order") defs''.values
then sortProperties defs''.values
else defs''.values;
in {
values = defs''';
inherit (defs'') highestPrio;
};
defsFinal = defsFinal'.values;
# Type-check the remaining definitions, and merge them. Or throw if no definitions.
mergedValue =
if isDefined then
if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
else let allInvalid = filter (def: ! type.check def.value) defsFinal;
in throw "A definition for option `${showOption loc}' is not of type `${type.description}'. Definition values:${showDefs allInvalid}"
else
# (nixos-option detects this specific error message and gives it special
# handling. If changed here, please change it there too.)
throw "The option `${showOption loc}' is used but not defined.";
isDefined = defsFinal != [];
optionalValue =
if isDefined then { value = mergedValue; }
else {};
};
/* Given a config set, expand mkMerge properties, and push down the
other properties into the children. The result is a list of
config sets that do not have properties at top-level. For
example,
mkMerge [ { boot = set1; } (mkIf cond { boot = set2; services = set3; }) ]
is transformed into
[ { boot = set1; } { boot = mkIf cond set2; services = mkIf cond set3; } ].
This transform is the critical step that allows mkIf conditions
to refer to the full configuration without creating an infinite
recursion.
*/
pushDownProperties = cfg:
if cfg._type or "" == "merge" then
concatMap pushDownProperties cfg.contents
else if cfg._type or "" == "if" then
map (mapAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
else if cfg._type or "" == "override" then
map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
else # FIXME: handle mkOrder?
[ cfg ];
/* Given a config value, expand mkMerge properties, and discharge
any mkIf conditions. That is, this is the place where mkIf
conditions are actually evaluated. The result is a list of
config values. For example, ‘mkIf false x’ yields ‘[]’,
‘mkIf true x’ yields ‘[x]’, and
mkMerge [ 1 (mkIf true 2) (mkIf true (mkIf false 3)) ]
yields ‘[ 1 2 ]’.
*/
dischargeProperties = def:
if def._type or "" == "merge" then
concatMap dischargeProperties def.contents
else if def._type or "" == "if" then
if isBool def.condition then
if def.condition then
dischargeProperties def.content
else
[ ]
else
throw "‘mkIf’ called with a non-Boolean condition"
else
[ def ];
/* Given a list of config values, process the mkOverride properties,
that is, return the values that have the highest (that is,
numerically lowest) priority, and strip the mkOverride
properties. For example,
[ { file = "/1"; value = mkOverride 10 "a"; }
{ file = "/2"; value = mkOverride 20 "b"; }
{ file = "/3"; value = "z"; }
{ file = "/4"; value = mkOverride 10 "d"; }
]
yields
[ { file = "/1"; value = "a"; }
{ file = "/4"; value = "d"; }
]
Note that "z" has the default priority 100.
*/
filterOverrides = defs: (filterOverrides' defs).values;
filterOverrides' = defs:
let
getPrio = def: if def.value._type or "" == "override" then def.value.priority else defaultOverridePriority;
highestPrio = foldl' (prio: def: min (getPrio def) prio) 9999 defs;
strip = def: if def.value._type or "" == "override" then def // { value = def.value.content; } else def;
in {
values = concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
inherit highestPrio;
};
/* Sort a list of properties. The sort priority of a property is
defaultOrderPriority by default, but can be overridden by wrapping the property
using mkOrder. */
sortProperties = defs:
let
strip = def:
if def.value._type or "" == "order"
then def // { value = def.value.content; inherit (def.value) priority; }
else def;
defs' = map strip defs;
compare = a: b: (a.priority or defaultOrderPriority) < (b.priority or defaultOrderPriority);
in sort compare defs';
# This calls substSubModules, whose entire purpose is only to ensure that
# option declarations in submodules have accurate position information.
# TODO: Merge this into mergeOptionDecls
fixupOptionType = loc: opt:
if opt.type.getSubModules or null == null
then opt // { type = opt.type or types.unspecified; }
else opt // { type = opt.type.substSubModules opt.options; options = []; };
/*
Merge an option's definitions in a way that preserves the priority of the
individual attributes in the option value.
This does not account for all option semantics, such as readOnly.
Type:
option -> attrsOf { highestPrio, value }
*/
mergeAttrDefinitionsWithPrio = opt:
let
defsByAttr =
lib.zipAttrs (
lib.concatLists (
lib.concatMap
({ value, ... }@def:
map
(lib.mapAttrsToList (k: value: { ${k} = def // { inherit value; }; }))
(pushDownProperties value)
)
opt.definitionsWithLocations
)
);
in
assert opt.type.name == "attrsOf" || opt.type.name == "lazyAttrsOf";
lib.mapAttrs
(k: v:
let merging = lib.mergeDefinitions (opt.loc ++ [k]) opt.type.nestedTypes.elemType v;
in {
value = merging.mergedValue;
inherit (merging.defsFinal') highestPrio;
})
defsByAttr;
/* Properties. */
mkIf = condition: content:
{ _type = "if";